In a chain drive such as the timing drive of automobile engine, slack in the chain can be removed, and vibration can be prevented, by a pivoted tensioner lever comprising a lever having a shoe surface in sliding contact with the chain. In such a tensioner lever, the shoe surface can be pressed against the chain by a coiled torsion spring interposed between the lever and a mounting surface.
A typical example of such a tensioner lever is shown in FIGS. 7 and 8, and described in U.S. Pat. No. 6,428,435, granted on Aug. 6, 2002. In the tensioner lever 500, an internal space 502B accommodates the wound portion 531 of a coiled torsion spring 530. The tensioner lever is formed with an opening 502A, through which the spring 530 can be incorporated into the internal space 502B. A boss 503, having an outer circumferential surface F, on which the wound portion 531 of the spring fits loosely, extends into space 502B from an outer wall of the lever. An arm 533 of the spring extends through a cut-out portion T in a part of the wall of the lever surrounding the coil spring. A laterally protruding end of the arm 533 extends into a hole h in a mounting surface R so that the end of the arm 533 is fixed, and torque can be exerted by the opposite end of the spring, urging the shoe surface S of the lever against a chain. The coil spring 530 can be incorporated into the lever 501 before the lever is mounted on mounting surface R.
In the process of mounting the conventional lever of FIGS. 7 and 8 on a mounting surface, the coil spring is first incorporated into the lever. Then, the protruding end of spring arm 533 is inserted into hole h in the mounting surface. The strong force exerted by the spring makes it difficult to align the shaft hole H in the boss with a hole N provided in the mounting surface R for receiving a mounting bolt 510. A related problem arises when the lever is mounted before the installation of the chain. The lever can be mounted without difficulty, but the spring causes the lever to pivot in a direction such that it interferes with the installation of the chain.
An object of the invention is to solve the above-described problem or by providing a spring-operated tensioner lever which can be mounted more easily.